Are mri's necessary? Muscle Contusion

Dear Ask The Doctor: I received an impact injury to my shin,about an inch above my ankle,10 days ago.the bruising has encompassed my about half of my lower leg,and most of my foot,but is healing normally.the sweeling was extreme,to the point where i couldnt bend my ankle.it has subsided,however a large knot remains to the right of the impact.there is minimal pain when i wiggle my toes,or raise my heel.x-rays were normal.what could be the cause of the large knot?

Dear Karyn: Contusions are second only to strains as a leading cause of active people and atletes injuries. Most contusions are minor and heal quickly. But, severe contusions can cause deep tissue damage and can lead to complications and/or take months for healing. Contusions occur when a direct blow or repeated blows from a blunt object strike part of the body, crushing underlying muscle fibers and connective tissue without breaking the skin. A contusion can result from falling or jamming the body against a hard surface. Sometimes a pool of blood collects within damaged tissue, forming a lump over the injury (hematoma) which can take some time to resolve. A physical examination will determine the exact location and extent of injury. Diagnostic imaging tools may be used to better visualize inside the injured area of your body. These tools include ultrasound, magnetic resonance imaging (MRI), or computed tomography (CT) scans. For some injuries, your doctor may also need to check for nerve injury. Contusions cause swelling and pain and limit joint range of motion near the injury. Torn blood vessels may cause bluish discoloration. The injured muscle may feel weak and stiff. To control pain, bleeding, and inflammation, keep the muscle in a gentle stretch position and use the RICE formula: Rest: Protect the injured area from further harm by stopping play. You may also use a protective device (i.e., crutches, sling). Ice: Apply ice wrapped in a clean cloth. (Remove ice after 20 minutes.). Compression: Lightly wrap the injured area in a soft bandage or ace wrap. Elevation: Raise it to a level above the heart. If there is a large hematoma that does not go away within several days, in some cases the doctor may drain it surgically to speed healing.